(1) Field of the Invention
This invention relates to a metal-made carrier body for an exhaust gas cleaning catalyst which is generally interposed as an exhaust gas cleaning means at an intermediary point in an exhaust gas system of an automotive vehicle. More specifically, this invention is concerned with a metal-made carrier body for an exhaust gas cleaning catalyst, which makes use of a means for efficiently converting streams of an exhaust gas into turbulent flows, thereby enhancing the cleaning efficiency of the exhaust gas.
(2) Description of the Related Art
With a view toward increasing the catalyst-carrying area per unit volume and at the same time reducing their own weights, metal-made carrier bodies for carrying an exhaust gas cleaning catalyst of the above sort have heretofore been manufactured by superposing at least one planar band and at least one corrugated band, each of said bands being made of a heat-resistant steel sheet of an extremely small thickness not greater than 0.1 mm, one over the other and then rolling them together into a spiral form or as an alternative, arranging them in layers, thereby forming a multi-layered composite body defining many network-patterned gas flow passages in a common direction, and thereafter enclosing the multi-layered composite body in a metal-made casing which is open at both ends thereof.
A great deal of work has recently been conducted with respect to metal-made carrier bodies of the above sort to improve the efficiency of contact between an exhaust gas and a catalyst and hence to enhance the cleaning efficiency. For example, Japanese Utility Model Laid-Open 90742/1987 discloses a carrier body formed of a planar metal band and a corrugated metal band, through each of which plural holes of about 0.5-10 mm in diameter are formed at a concentration of from 1 to about 10 holes per cm.sup.2.